CT scans are a fast, effective and accurate way of assisting your doctor to make a diagnosis and treat your condition.

CT is a way of using x-rays to take pictures or images in very fine slices through a part of your body that your doctor has asked to be investigated. Modern CT scanners are fast and our staff minimises radiation doses as much as possible.

Each scan is created specifically for the part of the body of interest and the condition that needs investigation. These images assist the radiologist (a doctor who has specialised in diagnostic imaging) in diagnosing your health problems.

How to prepare

You will receive instructions from our staff prior to your appointment. If you are an inpatient in the hospital, the nurses caring for you will ensure that the appropriate preparations are carried out. These instructions are very important as they may affect the accuracy of the test.

Some tests require no preparation. These include: brain, sinus, spine and scans of the bones.

Many types of CT scans require an injection of an iodinated contrast material to show blood vessels and some organs. For these scans you will need to fast for 2-4 hours and to drink water over a one hour period prior to your appointment time. It is important that the need to fast does not affect you if you have special dietary requirements (e.g. diabetes). Please check with your doctor or our website for more information.

While the iodinated contrast used for injections is considered very safe, there are precautions that must be taken when using it, particularly if you have poor kidney function, diabetes or if you have known allergy to iodinated contrast. If you have any concerns you should contact North Shore Radiology and Nuclear Medicine on 02 8425 3666.

It is important to follow the instructions you are given to ensure that the scan is done safely, accurately and efficiently, so that you do not need to have the scan rescheduled or repeated.


How long does it take?

Each scan is different and so the time it takes to complete will vary depending upon why you are having it. Generally most CT scans are completed in 5 to 20 minutes.

What to expect?

The CT scanner is a large square machine, or gantry, with a circular hole sometimes described as looking like a “donut”. The general process involves you lying on a bed attached to the scanner and the bed slides in and out of the hole several times while pictures are being taken. The radiographer performing the scan may ask you to hold your breath for some scans. The length of time for each breath hold is usually under 10 seconds. If you do require an iodinated contrast injection for your scan, a radiographer or a nurse will discuss iodine contrast with you. They will then use a needle to insert a cannula (a small plastic tube) into a vein in your arm or the back of your hand so that the iodine contrast can be injected into the cannula during the scan, usually by an automated injector. Once the radiographer has reviewed the images briefly to check that the appropriate areas have been shown, they will come into the room to remove the cannula and help you off the bed. The radiographer will not be able to give you any results after the scan; this is the responsibility of your doctor and the radiologist who interprets the pictures from the scan and provides a report to your doctor.


The vast majority of people who have a CT scan have no after effects at all. After the scan you may resume your normal diet and activities. In very uncommon cases, some people may be allergic to the iodinated contrast given into the vein in your arm or the back of your hand. It is not possible to predict if a person will be allergic to the iodinated contrast, though our staff are well trained to deal with allergic reactions should they arise. It is important to make the radiographer or nurse aware of any other allergies that you may have, prior to having the injection. People who are allergic to the iodinated contrast used in CT may get some of the following symptoms: • Nausea and/or vomiting • A skin rash or hives • Itching • Sneezing and/or watering eyes • Dizziness and/or headache • Gagging or feeling of suffocation or swelling of the inside of the throat or mouth • Change in blood pressure If you do feel any of these symptoms after your scan, it is important to tell the radiographer or nurse immediately. If these feelings come on after leaving our practice, you should return to us immediately (if this is close by) or attend the nearest doctor or emergency department.